Semiconductor integrated circuit

ABSTRACT

Provided is a semiconductor integrated circuit that improves insulation reliability between a high-voltage circuit and a low-voltage circuit. The semiconductor integrated circuit includes the following: a first circuit controlled by a control signal of low voltage and driven at a higher voltage; a second circuit configured to output the control signal to the first circuit to control the driving of the first circuit; and a plurality of insulation circuits each including an insulating element, the plurality of insulation circuits connecting between the first and the second circuits in series. Each insulation circuit is configured to magnetically or capacitively couple the control signal in the insulating element to transmit it from the second circuit to the first circuit, and is configured to insulate the first circuit from the second circuit in the insulating element to prevent the higher voltage from being applied from the first circuit to the second circuit.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to semiconductor integrated circuits.

Description of the Background Art

Insulation circuits (isolators) each have been conventionally interposedbetween a central processing unit (CPU) forming a control circuitpositioned at a higher level of a system, and a semiconductor switchingelement driven at a high voltage in the system. For instance, JapanesePatent Application Laid-Open No. 2013-51547 discloses a semiconductorintegrated circuit including an insulation circuit, such as aphotocoupler or a digital isolator. The semiconductor integrated circuittransmits a signal while insulating a transmission circuit from areception circuit.

The photocoupler or the digital isolator has an insulating portioncomposed of an organic compound. Applying a voltage equal to or greaterthan a dielectric strength across the insulating portion within theisolator produces an electrical breakdown to pass a short-circuitcurrent through the insulating portion. The CPU, disposed at a higherlevel of the system, and the inside of the system to which a highvoltage is applied are unfortunately no longer insulated from eachother.

SUMMARY

It is an object of the Specification to provide a semiconductorintegrated circuit that improves insulation reliability between acircuit driven at a high voltage and a circuit driven at a lower voltagethan the high voltage.

An aspect of the Specification provides a semiconductor integratedcircuit that includes the following: a first circuit controlled by acontrol signal of low voltage and driven at a higher voltage than thecontrol signal of low voltage; a second circuit configured to output thecontrol signal of low voltage to the first circuit to control thedriving of the first circuit; and a plurality of insulation circuitseach including an insulating element, the plurality of insulationcircuits connecting between the first circuit and the second circuit inseries. Each insulation circuit is configured to magnetically couple orcapacitively couple the control signal in the insulating element totransmit the control signal from the second circuit to the firstcircuit, and is configured to insulate the first circuit from the secondcircuit in the insulating element to prevent the higher voltage frombeing applied from the first circuit to the second circuit.

The semiconductor integrated circuit according to the aspect of theSpecification improves insulation reliability between a circuit drivenat a high voltage and a circuit driven at a lower voltage than the highvoltage.

These and other objects, features, aspects and advantages of the presentinvention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a configuration of a semiconductor integratedcircuit according to a first preferred embodiment;

FIG. 2 is a diagram of a configuration of a semiconductor integratedcircuit according to a second preferred embodiment;

FIG. 3 is a diagram of a configuration of a semiconductor integratedcircuit according to a third preferred embodiment;

FIG. 4 is a diagram of a configuration of a semiconductor integratedcircuit according to a fourth preferred embodiment; and

FIG. 5 is a diagram of a configuration of a semiconductor integratedcircuit according to a fifth preferred embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

<First Preferred Embodiment>

The following describes a semiconductor integrated circuit according toa first preferred embodiment. FIG. 1 is a diagram of a configuration ofthe semiconductor integrated circuit according to the first preferredembodiment.

The semiconductor integrated circuit includes a first circuit 10, asecond circuit 20, and a plurality of insulation circuits 30.

The first circuit 10 includes a switching element, and is disposed at alower level of a system (not shown). The first circuit 10 receives acontrol signal of low voltage from the second circuit 20, and is drivenat a higher voltage than the control signal of low voltage. Theswitching element outputs the high voltage in response to the receptionof the control signal of low voltage for instance. In the firstpreferred embodiment, the switching element is a semiconductor devicecalled a power semiconductor device to which the high voltage isapplied.

The second circuit 20 is disposed at a higher level of the system, andis a CPU for instance. The second circuit 20 outputs the control signalof low voltage to the first circuit 10 to control the driving of thefirst circuit 10.

Each insulation circuit 30 connects between the first circuit 10 and thesecond circuit 20 in series. In the first preferred embodiment, N numberof insulation circuits 30 ranging from n=1 to n=N are connected inseries is a natural number equal to or greater than one).

Each insulation circuit 30 includes an insulating element, which is notshown in FIG. 1.

Each insulation circuit 30 magnetically couples or capacitively couplesthe control signal in the insulating element to transmit the controlsignal from the second circuit 20 to the first circuit 10. Further, theinsulation circuit 30 insulates the first circuit 10 from the secondcircuit 20 in the insulating element to prevent the higher voltage frombeing applied from the first circuit 10 to the second circuit 20.

Even if an electrical breakdown is produced in the insulating elementincluded in any of the insulation circuits, the semiconductor integratedcircuit enables the remaining insulation circuits to securely insulatethe first circuit 10 from the second circuit 20. Moreover, thesemiconductor integrated circuit enables the system to which the highvoltage is applied and components including the CPU driven at the lowervoltage than the high voltage to be securely insulated from each other.That is, the semiconductor integrated circuit in the first preferredembodiment improves insulation reliability between the second circuit20, driven at the high voltage, and the first circuit 10, driven at thelower voltage than the high voltage.

<Second Preferred Embodiment>

The following describes a semiconductor integrated circuit according toa second preferred embodiment. It is noted that similar components andsimilar operations between the first preferred embodiment and the secondpreferred embodiment will not be elaborated upon here.

FIG. 2 is a diagram of a configuration of the semiconductor integratedcircuit according to the second preferred embodiment.

At least one of a plurality of insulation circuits 30 connecting betweenthe first circuit 10 and the second circuit 20 in series includes amagnetic coupling element 41 as an insulating element. In the secondpreferred embodiment, two insulation circuits 31 connect between thefirst circuit 10 and the second circuit 20 in series. Each insulationcircuit 31 is a digital isolator for instance. The magnetic couplingelement 41 is a transformer for instance. The number of insulationcircuits 31 for serial connection is not limited to two. N number ofinsulation circuits 31 may be connected in series.

Each insulation circuit 31 magnetically couples the control signaloutput from the second circuit 20 in the magnetic coupling element 41 totransmit the control signal to the first circuit 10.

A serial connection between insulation circuits can produce a delay insignal transmission in accordance with the number of insulation circuitsas connected in series, However, in the semiconductor integrated circuitin the second preferred embodiment, the transformer that is the magneticcoupling element 41 operates at a very high frequency, and thus thedelay in signal transmission is reduced.

<Third Preferred Embodiment>

The following describes a semiconductor integrated circuit according toa third preferred embodiment. It is noted that similar components andsimilar operations between the first or second preferred embodiment andthe third preferred embodiment will not be elaborated upon here.

FIG. 3 is a diagram of a configuration of the semiconductor integratedcircuit according to the third preferred embodiment

At least one of a plurality of insulation circuits 30 connecting betweenthe first circuit 10 and the second circuit 20 in series includes acapacitive coupling element 42 as an insulating element. In the thirdpreferred embodiment, two insulation circuits 32 connect between thefirst circuit 10 and the second circuit 20 in series. Each insulationcircuit 32 is a digital isolator for instance. The capacitive couplingelement 42 is a capacitor for instance. it is noted that the number ofinsulation circuits 32 for serial connection is not limited to two. Nnumber of insulation circuits 32 may be connected in series.

Each insulation circuit 32 capacitively couples the control signaloutput from the second circuit 20 in the capacitive coupling element 42to transmit the control signal to the first circuit 10.

In the semiconductor integrated circuit, a capacity forming thecapacitive coupling element 42, e.g., the thickness of an insulatingfilm facilitates the control of a dielectric strength.

<Fourth Preferred Embodiment>

The following describes a semiconductor integrated circuit according toa fourth preferred embodiment. It is noted that similar components andsimilar operations between any of the first to third preferredembodiments and the fourth preferred embodiment will not be elaboratedupon here.

FIG. 4 is a diagram of a configuration of the semiconductor integratedcircuit according to the fourth preferred embodiment.

At least one of a plurality of insulation circuits 30 connecting betweenthe first circuit 10 and the second circuit 20 in series includes themagnetic coupling element 41 as an insulating element. Moreover, atleast another of the plurality of insulation circuits 30 includes thecapacitive coupling element 42 as an insulating element. That is, thesemiconductor integrated circuit includes a combination of an insulationcircuit 31 including the magnetic coupling element 41 and an insulationcircuit 32 including the capacitive coupling element 42.

A single insulation circuit 31 and a single insulation circuit 32connect between the first circuit 10 and the second circuit 20 inseries. It is noted that the number of insulation circuits 30 for serialconnection is not limited to two. N number of insulation circuits 30 maybe connected in series.

The insulation circuit 31 magnetically couples the control signal outputfrom the second circuit 20 in the magnetic coupling element 41 totransmit the control signal to the first circuit 10. Moreover, theinsulation circuit 32 capacitively couples the control signal in thecapacitive coupling element 42 to transmit the control signal to thefirst circuit 10.

With such a configuration, the magnetic coupling element 41 prevents theincrease or the generation of the delay in signal transmission. Inaddition, a transmission-and-reception mode of a transformer, which isthe magnetic coupling element 41, facilitates the control of acommon-mode transient immunity (CMTI) or noise tolerance. In addition,controlling the thickness of an insulating film of the capacitivecoupling element 42 obtains a desired dielectric strength.

<Fifth Preferred Embodiment>

The following describes a semiconductor integrated circuit according toa fifth preferred embodiment. It is noted that similar components andsimilar operations between any of the first to fourth preferredembodiments and the fifth preferred embodiment will not be elaboratedupon here.

FIG. 5 is a diagram of a configuration of the semiconductor integratedcircuit according to the fifth preferred embodiment.

A first circuit 10 includes a switching element 11. The switchingelement 11 is a semiconductor device formed of a transistor containingSiC and called a power semiconductor device to which a high voltage isapplied. Herein, the switching element 11 is a SiCmetal-oxide-semiconductor field-effect transistor (MOSFET).

A second circuit 20 outputs the control signal to the switching element11 to control the driving of the switching element 11 to control thedriving of the first circuit 10.

A power semiconductor device, such as a SiC MOSFET provides highperformance in an application requiring high-speed operation or anapplication requiring high strength. In the fifth preferred embodiment,the semiconductor integrated circuit includes a plurality of insulationcircuits 30, such as digital isolators having high-insulationperformance and high-speed performance. This improves a system levelwhen the semiconductor integrated circuit controls the driving of thepower semiconductor device.

It is noted that in the present invention, the individual embodimentscan be freely combined, or can be modified and omitted as appropriate,within the scope of the invention. While the invention has been shownand described in detail, the foregoing description is in all aspectsillustrative and not restrictive. It is therefore understood thatnumerous modifications and variations can be devised without departingfrom the scope of the invention.

What is claimed is:
 1. A semiconductor integrated circuit comprising: afirst circuit controlled by a control signal of low voltage and drivenat a higher voltage than the control signal of low voltage; a secondcircuit configured to output the control signal of low voltage to thefirst circuit to control driving of the first circuit; and a pluralityof insulation circuits each including an insulating element, theplurality of insulation circuits connecting between the first circuitand the second circuit in series, wherein each insulation circuit isconfigured to magnetically couple or capacitively couple the controlsignal in the insulating element to transmit the control signal from thesecond circuit to the first circuit, and is configured to insulate thefirst circuit from the second circuit in the insulating element toprevent the higher voltage from being applied from the first circuit tothe second circuit.
 2. The semiconductor integrated circuit according toclaim 1, wherein at least one of the plurality of insulation circuitsincludes, as the insulating element, a magnetic coupling elementconfigured to magnetically couple the control signal.
 3. Thesemiconductor integrated circuit according to claim 1, wherein at leastone of the plurality of insulation circuits includes, as the insulatingelement, a capacitive coupling element configured to capacitively couplethe control signal.
 4. The semiconductor integrated circuit according toclaim 1, wherein at least one of the plurality of insulation circuitsincludes, as the insulating element, a magnetic coupling elementconfigured to magnetically couple the control signal, and at leastanother of the plurality of insulation circuits includes, as theinsulating element, a capacitive coupling element configured tocapacitively couple the control signal.
 5. The semiconductor integratedcircuit according to claim 1, wherein the first circuit includes aswitching element, the second circuit is configured to output thecontrol signal to the switching element to control driving of theswitching element to control the driving of the first circuit, and theswitching element is a semiconductor device formed of a transistorcontaining SiC.